Seasonal variations of soil functions affected by straw incorporation in croplands with different degradation degrees

The reduction of soil function in croplands is widespread over the world resulting from land degradation induced by intensified agricultural practices. Straw incorporation likely affects soil function in sloping croplands. However, the quantitative influences of incorporated straw on the seasonal dynamics of soil function in croplands with different degradation degrees are still uncertain. The objective of the study is to identify the seasonal variations of different soil functions affected by straw incorporation in different degraded croplands in the black soil region of China. The results of network analysis denoted that soil functions could be fully quantified by eight factors. They were water-stable aggregate, available nitrogen, available phosphorus, humin acid, cation exchange capacity, soil organic matter, invertase and catalase. Significant seasonal variations were observed in soil function factors of different degraded croplands under straw incorporation treatment and its control (p < 0.05). Correspondingly, soil functions exhibited significant seasonal variations in various degraded croplands (p < 0.05). Soil functions were greatly enhanced by incorporated straw. In comparison to the without straw incorporation treatment, soil functions increased by 0.8 %-47.4 % during the growing season. The promotions in soil functions by straw incorporation were closely related to land degradation degree. Compared to cropland of non-degradation, the enhancements of soil functions declined by 6.2 %-58.5 %, 6.5 %-81.7 % and 11.7 %-95.2 % in the light, moderate and strong degradation croplands, respectively. Incorporated straw stimulated crop growth by improving soil functions and the crop yield increased by 12.7 %-18.7 %. Straw incorporation enhances soil functions and crop growth via improved water-stable aggregate, soil organic matter, cation exchange capacity and humin acid of different degraded croplands. The results highlight the significance of straw incorporation in degraded croplands to ameliorate soil functions and crop growth in intensive agricultural regions.